This is a plain English summary of an original research article
Minimally invasive surgery to repair abdominal aortic aneurysm (AAA) was associated with fewer aneurysm-related deaths in the short-term, up to six months. From eight years onwards the open surgical procedures were associated with fewer aneurysm-related deaths, suggesting on-going monitoring is required.
An AAA is a swelling due to weakness in the main blood vessel running through the centre of the abdomen. If the aneurysm bursts there is a high chance of death. Earlier trials suggested that the minimally invasive technique of endovascular aneurysm repair (EVAR) gave mortality benefits in the immediate months after the procedure, but this was lost after a few years.
This trial is the longest follow-up trial of aneurysm repair using either endovascular or open surgery techniques. Patient factors including age, health and aneurysm size, may affect the outcome with either procedure. These factors, along with expected recovery time and potential complications, should inform surgical choices and guide the process of informed consent.
Why was this study needed?
An AAA usually does not cause any symptoms unless it ruptures. This results in massive bleeding which is fatal for 8 out of 10 people. A ruptured aneurysm causes 1 in 50 deaths amongst men aged 65 and over in the UK so men above this age are offered one-off ultrasound screening.
If a small to medium size aneurysm is found (between 3.0 and 5.4cm diameter), regular follow-up monitoring is offered. If the aneurysm is large (5.5cm or more) they will be offered surgery to repair the aneurysm.
There are two main methods for aneurysm repair, either open surgery or minimally invasive endovascular repair (EVAR). Previous trials suggested short-term mortality benefits of EVAR that diminished in the following years. Therefore this trial focused on longer term outcomes.
What did this study do?
The UK endovascular aneurysm repair trial 1 (EVAR-1) recruited 1252 people with large AAA aged 60 years and over from 37 UK hospitals (1999 to 2004). Most participants were men (91%) with average age 74 years.
Participants were randomly allocated to receive either open or minimally invasive endovascular aneurysm repair. They received annual check-ups for an average 12.7 years. The main outcome of interest was overall mortality and aneurysm-related mortality. This included deaths from rupture before or after the primary or subsequent procedures, or other related causes, such as graft infection.
All randomised patients were included in the analysis and the study had sufficient sample size to reliably detect differences in the main outcomes.
What did it find?
- There were differences in aneurysm-related mortality at different time points.
- Up to six months after the procedure there were fewer aneurysm-related deaths in the EVAR group, with 4.6 deaths per 100 per year compared with 10 per 100 per year amongst those undergoing open repair (adjusted hazard ratio [HR] 0.47, 95% CI 0.23 to 0.93).
- There was no significant difference in aneurysm-related mortality between six months and up to eight years. However, from eight years onwards the situation had reversed and the risk of aneurysm-related death was higher among the EVAR group (1.3 per 100 per year) compared with open repair participants (0.2 per 100 per year; adjusted HR 5.82, 95% CI 1.64 to 20.65).
- From eight years onwards there were also slightly more deaths from any cause in the EVAR group (14.9 vs. 12.7 per 100 per year) but this was on the borderline of reaching statistical significance (adjusted HR 1.25, 95% CI 1.00 to 1.56).
What does current guidance say on this issue?
NICE is in the process of producing a guideline on the diagnosis and management of abdominal aortic aneurysm, which is due for publication in November 2018. NICE has approved EVAR as a procedure. It recommends that the choice between an open or endovascular approach is based on patient factors (such as age and aneurysm size) and that clinicians discuss the uncertainties about longer-term outcomes with patients to ensure their informed consent.
What are the implications?
The findings of this large trial support the findings of earlier trials that there may be short-term advantages to stenting, but these aren’t sustained and open repair has better mortality outcomes in the longer term. The authors suggest this indicates a need for structured surveillance of stent recipients to ensure that further procedures, if needed, can be performed as quickly as possible. They point out that recent changes to the design of these stents may also help.
Previous study found that patients prefer stents due to recovery time and complications, and this is often the procedure of choice. The combined findings highlight the importance of informed patient choice when deciding between open and stenting procedures.
Citation and Funding
Patel R, Sweeting MJ, Powell JT, Greenhalgh RM; EVAR trial investigators. Endovascular versus open repair of abdominal aortic aneurysm in 15-years' follow-up of the UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial. Lancet. 2016;388(10058):2366-74.
This project was funded by the National Institute for Health Research Health Technology Assessment Programme (project number 11/36/46).
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